The field of the present invention relates to a data processor for processing a data stream having audio and video data, and to a method for processing a data stream having audio and video data, such as the ones used for presenting a multimedia content stored on an information carrier.
Home entertainment has become a popular pastime for many people since its introduction in the late 1970s, when home video became available to the wide public in the form of video home system (VHS) or Betamax video cassettes. The terms home video and home entertainment nowadays comprise current optical disc formats like Digital Versatile Disc (DVD) and Blu-ray (BD) disc. The home video industry also comprises methods of digital distribution of pre-recorded media over a communications network, such as video-on-demand. The DVD format has become one of the most popular formats for the distribution of theatrically released films. The Blu-ray disc format may be regarded as a successor to the DVD format.
While dedicated DVD players or Blu-ray disc players exist, it is typically also possible to use a standard personal computer (PC) equipped with a suitable DVD reader or Blu-ray disc reader. In a large number of cases, these PCs are equipped with a standard operating system that is not dedicated to handle real-time tasks. In a non-real time operating system it cannot be predicted when a certain task will be performed, because a scheduling of a task depends heavily on the current system load. In order to cope with a variable system load, current solutions for DVD or Blu-ray disk playback on a PC resort to buffering large amounts of data in the stream processor, or upstream thereof, to allow a smooth playback of audio and video data. The buffer provides a constant data stream to the stream processor in a manner substantially independent from the current system load. This scheme works as long as the buffer knows or can predict, at the time of buffering certain data, which type of data will be needed at a time of retrieving the buffered data from the buffer.
Especially with the DVD and Blu-ray disc formats, the user typically has a choice of two or more languages for an audio track or a subtitle to be played or displayed along with a video track of the audiovisual presentation. If the user changes the audio or subtitle language, a noticeable delay occurs (4-5 seconds) because the already buffered data (with the previous language settings) will be presented first before the new data stream reaches the display or the speakers connected to the personal computer.
In low latency hardware implementations or in dedicated real-time operating system environments, the delay observed when switching the audio track or the subtitle from one language to another, is typically hardly noticeable, because such implementations do not need to use large buffers.